[tex] \left \{ {{-7x-2y=-13} \atop {x-2y=11}} \right. \\\\ \left \{ {{-7x-2y=-13} \atop {x=11+2y}} \right.\\\\
Substitute\ second\ equation\ into\ the\ first\ one:\\\\
-7(11+2y)-2y=-13\\
-77-14y-2y=-13\\
-77-16y=-13\ \ \ |Add\ 77\\
-16y= 64\ \ \ |Divide\ by\ -16\\
y=-4\\\\x=11+2y=11+2*(-4)=11-8=3\\\\ \left \{ {{y=-4} \atop {x=3}} \right. [/tex]
